Police wait outside an apartment early Tuesday, Aug. 26, 2014, in Tulsa, Okla. where authorities say where four people, including two young children, have been shot to death in a possible triple murder-suicide. (AP Photo/Tulsa World, Tom Gilbert)

TULSA, Okla. (AP) — Four people, including two young children, were shot to death in a Tulsa apartment and detectives are investigating the case as a murder-suicide, police said Tuesday.

Police believe a 35-year-old man killed his estranged wife on Monday, along with their 5-year-old daughter and 3-year-old son, before shooting himself. A 2-year-old girl not related to the family was found apparently unharmed inside the apartment, Tulsa police said in a statement Tuesday.

The police statement said the family came from Guatemala but that authorities have no other details about their identities, including next of kin. Police spokeswoman Jillian Roberson said she had no further information on the case.

The surviving child was the daughter of the dead woman’s roommate, and she was inside the apartment when the shootings took place, police said. The girl has been reunited with her mother.

Neighbors at the Bradford Townhouses Apartments said the family killed was respectful and quiet, but that violent crime has become rampant in the area in recent years.

“They were great,” said caretaker Lonnie Chandler as he swept up beer bottle caps and shreds of the yellow police caution tape that had cordoned off the crime scene a few hours earlier. “Yesterday, they was sitting out on the patio, listening to music, smoking cigarettes.”

Chandler said he was raised on the South Side of Chicago and that he’s used to living in a violent part of town, but that the criminal activity around the townhomes — including drugs, prostitution and gang fights — was getting out of hand.

“It’s one thing after another going on here, and it’s just sad,” said Chandler’s wife, Wanda, as she helped to clean up.

“It’s time to go,” said another neighbor, Renee McKenzie, citing the violence in the area. She said she heard shots ring out a week earlier, peered out of her window and saw two cars speeding toward the complex.

“They just started shooting,” she said.

A lot of the people who hang out in the complex don’t even appear to belong there, McKenzie said.

“Half of the people who live over here,” she said, “you don’t even know if they live here or not.”